1. Field of the Invention
The present invention relates first to a method for measuring the injection quantity of injection systems, in particular in internal combustion engines, in which a test fluid is injected by the injection system into a measurement chamber.
2. Deascription of the Prior Art
One method known on the market uses an apparatus known as an EMI (injection quantity indicator). This indicator comprises a housing, in which a piston is guided. The interior of the housing and the piston define a measurement chamber. The measurement chamber has an opening against which an injection nozzle can be placed in a pressure-tight fashion. If the injection nozzle injects fuel into the measurement chamber, a fluid located in the measurement chamber is positively displaced. As a result, the piston moves, which is detected by a travel sensor. From the travel of the piston, a conclusion can be drawn about the change in volume of the measurement chamber, or in the fluid contained in it, and as a result about the injected fluid quantity.
The known method already functions with very high precision. Especially in internal combustion engines, however, more and more injection systems are being used that inject very tiny injection quantities, and in which the injections comprise a plurality of partial injections in rapid succession. In measuring such injections, even more-precise detection of the injection quantities may be wanted.
The present invention therefore has the object of refining a method of the type defined at the outset such that even the tiniest injection quantities can be measured with high precision. Even injections in rapid succession should be measurable with high reliability.
In a method of the type defined at the outset, this object is attained in that the volume of the measurement chamber is constant during the injection; a gas volume, preferably an air volume is present in the measurement chamber; and the injected volume of test fluid is ascertained, by means of the state equation for ideal gases, from the pressure change in the measurement chamber that results upon an injection.